patch 8.1.0888: the a: dict is not immutable as documented commit https://github.com/vim/vim/commit/31b816042fca879b11965ddd75287732563ba698 Author: Bram Moolenaar <Bram@vim.org> Date: Sun Feb 10 22:14:27 2019 +0100 patch 8.1.0888: the a: dict is not immutable as documented Problem: The a: dict is not immutable as documented. Solution: Make the a:dict immutable, add a test. (Ozaki Kiichi, Yasuhiro Matsumoto, closes #3929)